EFFECT OF A SEAWEED EXTRACT ON CITRUS FRUIT MATURATION

The effect of a seaweed extract application on fruit maturation was examined with two early ripening mandarins (Clausellina and Marisol) and the early ripening Navelina orange. An aqueous extract obtained from Ascophyllum nodosum and marketed under the trade-mark Goemar® was used throughout.

In the three cultivars that we studied, the application of the seaweed extract enhanced fruit earliness as measured by the maturity index (MI), calculated as the ratio of total soluble solids (TSS) to titratable acidity. Three full-cover sprays applied at the beginning of flower development, at full bloom, and at the end of the fruitlet drop period (June drop), applied at a concentration of 0.15%, gave the maximum response. Increasing the seaweed concentration or the number of applications did not improve the results. The maximum difference in MI between the treated and the control fruits was 0.5 points at the time of commercial ripening. This difference decreased afterwards as the fruit overripened. The increase was mostly due to the reduction in acidity, but an increase in TSS was recorded in some experiments. No effect was found on the juice content of the fruits.

The treated fruits could be harvested 5 to 7 days in advance to the control-untreated fruits. This circumstance results in an economic advantage for the early cropping cultivars, in which earliness results in a premium price in the market.